The present invention relates to photographic processing equipment. In particular, the present invention relates to an improved paper supply and drive system for use in an automatic photographic paper cutter.
In commercial photographic processing operations, very high rates of processing must be achieved and maintained in order to operate profitably. To expedite the photographic processing, orders containing film of similar type and size are spliced together for developing. As many as 500 to 1000 rolls of 12, 20, and 36 exposure film may be spliced together for processing and printing purposes.
After developing, the photographic images contained in the film negatives are printed in an edge-to-edge relationship on a continuous strip of photosensitive paper by a photographic printer. The photographic printer causes high intensity light to be passed through a negative and imaged on the photographic print paper. The photographic emulsion layer on the print paper is exposed and is subsequently processed to produce a print of the image contained in the negative.
After the strip of print paper has been photoprocessed to produce prints, a photographic paper cutter cuts individual prints from the strip. The prints are then sorted by customer order and ultimately packaged and sent to the customer.
A photographic paper cutter requires a paper supply and drive mechanism which withdraws the photographic paper strip from a roll and drives the paper to the knife assembly of the cutter. The desire for higher production has resulted in the development of automatic photographic paper cutters with increasingly higher speeds. For example, automatic paper cutters capable of cutting 25,000 prints per hour (i.e. over seven prints per second) are being developed. This places extreme demands on both the paper supply and paper drive mechanisms, and the need for improved paper supply and drive mechanisms becomes particularly apparent.
The drive mechanism of an automatic paper cutter must be capable of driving a paper strip extremely rapidly and accurately. Any inaccuracy in the drive mechanism may result in the photographic prints being cut at improper locations.
While the prior art drive mechanisms for photographic paper cutters have been generally satisfactory, they have had shortcomings. In particular, the typical prior art drive mechanism utilizes a drive roller in the center of the paper strip. This drive roller obscures the operator's view of the prints as they are moved toward the knife assembly. This is a particular disadvantage when the paper cutter is being used in conjunction with a print sorting apparatus, in which the prints which are cut are then sorted into good, remake, and reject categories.
In order for the paper drive mechanism to meet the stringent speed and accuracy requirements, the paper supply must supply the strip to the drive mechanism under essentially tension free or zero drag conditions. This requirement is complicated by the fact that the paper roll gets smaller as paper is withdrawn and, therefore, the weight of the roll and the resistance to withdrawal of paper from the roll is not constant. In the past, paper supply mechanisms have been developed which maintain a tension-free slack loop of the photographic paper strip between the supply roll and the drive mechanism. Examples of previous photographic paper supply mechanisms may be seen in U.S. Pat. No. 3,857,312 and 4,029,247.